The drugs are becoming more common in river waters and can play dangerous head games with fish
By Janet Raloff
TAMPA, Fla. — In the fish world, baby is just another word for lunch. So it behooves aquatic larvae to be ever vigilant. Yet those who as embryos or hatchlings encountered water polluted with trace concentrations of an antidepressant are much more likely to become lunch.
Tons of medicine ends up in the environment each year. Much has been excreted by patients. Leftover pills may also have been flushed down the toilet. Because water treatment plants were never designed to remove pharmaceuticals, water released into rivers by these plants generally carries a broad and diverse array of drug residues.
In 2006, a pair of chemists reported that antidepressants downstream of water treatment plants were making it into the brains of fish.
Meghan McGee of St. Cloud State University in Minnesota studies larval fathead minnows. Recently she set out to see whether exposure to specific antidepressants would affect the fish. Fish exposed as embryos or hatchlings to trace concentrations of the antidepressant venlafaxine, marketed as Effexor, didn’t react as quickly as normal to stimuli signaling a possible predator. This laid-back reaction could prove to be a “death sentence,” she observes.
McGee’s is one of many studies probing behavioral impacts on aquatic wildlife from pharmaceutical pollution, especially antidepressants. Emerging data from these studies were reported in Tampa, Fla. November 16-20 at the North America annual meeting of the Society of Environmental Toxicology and Chemistry, or SETAC. Overall, the studies show that antidepressants can impair a fish’s ability to eat, to avoid being eaten — and perhaps even to attract a mate.
And venlafaxine: It’s one of many antidepressants found in river waters. Indeed, McGee’s team selected concentrations for this study based on values measured downstream of water treatment plants.
“I was surprised how often I was seeing these antidepressants,” recalls Melissa Schultz of the College of Wooster in Ohio, one of the chemists who documented that antidepressants reach fish brains. “Pretty much any water sample in the vicinity of a waste water treatment plant will test positive for some group of antidepressants,” she finds.
The most common ones showing up in water: venlafaxine, bupropion — marketed as Wellbutrin, and citalopram — sold as Celexa. What showed up in fish brains were both the drugs and their metabolites, or breakdown products. “The most common ones we saw were metabolites of Prozac [fluoxetine] and Zoloft [sertraline],” Schultz says. The second most abundant were the parent compounds: Prozac and Zoloft. “So profiles of these drugs in the brain weren’t matching the profiles we were seeing in the water.” Why remains a mystery.
Explains Schultz: “When a fish is exposed to waste water, it’s not just getting a dose of antidepressants, it’s also encountering lots of other things” — including other drugs. In the future, she says, “we’ll have to look at how these might all interact.”
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